Rectifier for electric currents



Aug. 28, 1923..

. 1,466.541 M. MORRISON RECTIFIER FOR ELECTRIC CURRENT S Filed April 12 1921 3 Sheets-Sheet 1 INVENTOR Aug. 28, 1923.

M. MORRISON RECTIFIER FOR ELECTRIC CURRENTS April 12 Fil Aug. 28, [923.

M. MORRISON RECTIFIER FOR ELECTRIC CURRENTS Filed April 12 1921 s Sheets-Shut s R O T N E V m I Patented Aug, 28, 1923.

UNITED STATES PATENT oFFlcE.

MONTFORD MORRISON, OF NEW YORK, N. Y.

RECTIFIER FOR ELECTRIC CURREN'I'S.

Application filed April 12, 1921. Serial No. 460,835.

, T 0 all whom it may concern:

Be it known that I, MONTFORD MORRISON, citizen of the United States, resident of New York, county of New York, State of New York, have invented new and useful Improvements in Rectifiers for Electric Currents, of which the following is a spec fication.

My invention relates to improvements in electrical rectifiers.

The objects of my invention are, first, to provide an improved rectifier in WhlCh the various conductors and charged surfaces have effective radii of curvature at all points such as to substantially prevent the formation of corona, with the probable exception of the places where spark-over intentionally occurs, in which case it may be said that the object of my invention is to have practically no corona occur before spark-over; second,

to provide a construction which allows the amount of current-wave per cycle rectified to be varied by the initial construction of the device without increasing its size undesirably; third, to reduce the general proportions of the rectifier for a given voltage and output without decreasing the insulation factors; fourth, to reduce the arcing between stationary and revolving parts to a deslrable minimum; fifth, to produce a rectifier, which is as free as possible from useless corona discharge as the resultant atmospheric effects are detrimental to human health.

I attain these objects by the constructions shown in the accompanying drawings which illustrate several embodiments of my invention.

In said drawings, Fig. 1 is a circuit diagram; Fig. 2 is an end elevation, shown somewhat schematically, of a modified form of apparatus; Fig. 3 is a side elevation thereof; Fig. 4 is a side elevation of a commercial embodiment of the invention; Fig. 5 is an end elevation thereof.

In this specification I use two scientific terms homoeoid and toroid, of which I give the following definition The term homoeoid was introduced by Kelvin and Taits in their treatise on Natural Philosophy in their discussion of Abstract T dynamics and static and was defined as: An

infinitely thin shell bounded by twosimilar surfaces similarly oriented. They later refer to thick homoeoids which are shells of finite thickness. In the use of this word, covit encloses, is, of course, independent of the internal surface of the shell' and in my invention I am only concerned with the dis tribution of the outer surface and the efore the shell thickness plays no importan role and further, since I am only interested in and make use of these homoeoids for the external electrostatic field distribution which they are capable of influencing, the homoeoidal surface need not necessarily be entirely closed and may be segmental, may have openings and may have positive or negative radii of curvature or both. The only condition imposed upon its geometrical construc tion is that in the use to which I put this figure when in operation on my device, the electrostatic field which it is capable of influencing in conjunction with other parts of my apparatus, will be such as to substantially prevent corona before spark-over.

By the use of the word toroid I wish to disclose a more specific geometrical figure but it will be appreciated that the word homoeoid being a most general case of a geometrical figure, toroid will be necessarily a form of homoeoid. I wish, then, to limit the use of toroid to a figure generated by any plane curve moved in a direction at right angles to its plane surface; the path of the direction of which movement may obey any law Whatever. This definition is a little different from common generalized toroid in which the plane curve must revolve about the centre of a radius passing through the plane, that is the path of the direction limited to a circle.

Fig. 1 illustrates the general scheme of my invention in which 1 is a source of electromotive force to be transformed and this source may give any form of substantially periodically varying electro-motive .force suitable for rectification by my device and may be of a wave-form containing either odd harmonics, even harmonics or both, or even a constant term; when analyzed mathematically by the method of Fourier given in his Thorie Analytique de la Chaleur. This electro-motive force just described, is impressed upon primary terminals 4 and 5 of transformer 6 by means of leads 2 and 3. I have illustrated transformer 6 as a step-up transformer because of the nature of the load which I employ in the illustration, though I do not limit myself to the nature of the load nor to the employment of a transformer, nor to the voltage which I am capable of rectifying. By means of induction, there is impressed upon the secondary terminals? and 8 of transformer 6 an electromotive force suitable for rectification and which, transformer secondary forms a new source of voltage to which may refer as the source in which I am interested at. present. I lead this new electro-motive force by means of leads 9 and 10 to two 11 and 13,

of four substantially equally radially and circumferentially spaced general finite homoeoidswhich may have any shape whatever, so long as the effective radii of the curvature at all points is such as to substantially prevent corona before spark-over. These four finite homoeoids 11', 12, 13 and 14 work in conjunction with general homoeoids or preferably segmental toroids 15 and 16 which comprise segmental toroidal-surfaces with homoeoidal ends 17 and 18. The ends of the segmental surfaces give a generally closed figure but the only condition which is necessary for the operation of this device is that before mentioned and that is that the effective radii of curvature at all points will be such as to substantially prevent corona before spark-over. These segmental toroidhomoeoids are generated about axis 19 which is the center of a shaft 20 onto which is fixed an insulating disc 21 to which is fixed the toroid-homoeoids which revolve with shaft 20. From finite homoeoids 12 and 14 leads 22 and 23 conduct the rectified current to the load 24. In the operation of my device I employed means for rotating shaft 21 and hence homoeoid toroids 15 and 16 synchronously by any desirable means, such as direct connection with the alternator supplying the power or by means of a synchronous motor or other device. It will be appreciated by those familiar with the art to which my invention appertains that these finite homoeoidal surfaces acting in conjunction with each other, comprise a rectifying switch with the general properties of ability to rectify periodically varying current into uni-directional current and as such rectification is well known \in the art, this particular phase need not be elaborated on.

I also may employ leads to and from my rectifier having effective radii of curvature at all points such as to substantially prevent the formation of corona before spark-over.

By use .of the construction which I employ in my invention, I am able to construct a high tension rectifier which has no corona on any part of it with the possible exception of that between actual arcing points which are found between the stationary homoeoidal surfaces and revolving toroidal surfaces when no actual contact is employed.

It will be again appreciated by those skilled in the art to .which my invention appertains that these described toroidal segments may be replaced by general homoeoids of any shape whatever, provided the effective radii of curvature at all points is such as to substantially prevent corona before spark-over.

In the present description, I refer to one set of. geometrical figures as stationary and one set as revolving, though my invention works as well with this order reversed as in the described plan.

My invention has the further advantage of being made smaller in construction as it is well lmown that when the radii of curvature of high tension electrodes is increased, the spacings between electrodes of different polarity may be made shorter for the. same spark-over with even more definite sparkover values.

In View of this last mentioned fact, it will be readily understood that the length of the arcs 15 and 16, since they are of the construction outlined, may be made much longer and the distance 25 may be closer than in constructions heretofore made patent, because of the fact that I have substantially no corona before spark-over in my invention, and I may thus rectify, more or less of alternating current-wave as desired without increasing the over-all dimensions of the rectifier and in general, may decrease them.

And further, if contact is employed between revolving and stationary electrodes in my invention, almost sparkless, rectification may be obtained.

In the device just described, I find that in most insulating materials which I would utilize to fix the revolving parts to the shaft, and which insulating material is indicated by figure 21 in Fig. 1, the specific inductive capacity is such as to disturb the electrostatic field distribution between revolving toroidal segments 15 and 16 in such a way as to decrease the spark-over voltage to a value below that in air and in addition to which I find that moisture condensation and other collected and gaseous deposits on this insulating material may increase the electric surface leakage. In view of this, I disclose a second construction which I illustrate in Fig. 2 and Fig. 3 in which I employ substantially the same construction as illustrated in Fig. 1 with the exception that in Fig. 1 the toroidal segments 15 and 16 are represented as being in the same plane, and in Fig. 3 I have represented them as being in different planes and in each case I generally prefer to employ two sets of four each of the finite homoeoids 11, 12, 13 and 14:; one set in a plane in which segmental toroid 15 slightly less nected together to give substantially the same effect and results as described in Fig. 1

withthe difference that I have in Fig. 2 and Fig. 3 illustrated a device with much greater insulation between the toroidal segments, which in certain cases increases the insulation factor of my invention considerably though the operation is substantially the, same.

In the construction illustrated in Fig. 3 there are required bearings and 26'as well as supports and connections and so forth which-increase the cost of my device. In'Fig; 4v and Fig 5 of the illustration of the second modification of my invention which eliminates the additional bearings and utilizes the motor or alternator bearing and further ,utilizes motor frame for supporting the stationary homoeoids 11, 12, 13 and 14. It will 'be readily observed that Fig. 4 and Fig. 5 represent substantially the same device as illustrated in Fig. 2 and Fig. 3, the device being simply parted at point 27 in Fig. 3 and the motor or alternator 28 in Fig. 4 interposed between thesetwo elements.

Otherwise the device is substantially thev same.

In Fig. 4 and Fig. 5 I illustrate by 29 brush or other wiping contacts which are common in the general art of electrical en gineering and which may in certain cases, be employed to an advantage in my device.

It will be further appreciated that with the use of my invention, barrier between electrodes of different polarity may be eliminated with decreased dimensions though it maybe that in some cases I may desire to use barriers which are common in the art related to this clam of apparatus and in which case I can reduce thesize of my device still further.'

- It will be appreciated by those familiar .with he art to whichmy. invention appertains, that heretofore the arc length utilized in high'tension rectifiers hasbeen limited to a length corresponding with equal to or than that of the alternating current-wave. I

My device,for the first time, discloses the fact that the conducting arc of a high tension rectifier may be considerably longer than the alternating current wave and as a v theoreticalilimit, it may be twice as long particularly with a very large rectifier; this is not fiers. y

In reality, in myrectifier with conducting arcs of a length corresponding to slightly less than that of the alternating currentwave, I obtain a comparatively short duration of rectification, I must make my conducting arcs longer than the length of the alternating cu'rrentwave tofget any appre possible with heretofore disclosed recticiable duration of rectification, which con trasts strongly with devices heretofore disclosed. Tlns will be appreciated to be due to the fact that with the large radii of curvatures which I employ, the parts which move relatively toward each other have to approach very closely before spark-over occurs and the trailing arc is cut off earlier.

With the construction that I employ in my device, I am able to get extremely short duration of rectification much shorter \than possible by other means. That is in cases where desire to rectify only short intervals of waves, I may do this with more precision and with shorter duration than by other devices.

It will be appreciated that my device contrasts very sharply 'with other mechanical rectifiers -which have been heretofore disclosed in many respects and prinpipally in the fact that the lengths of my conducting arcs do not bear the same relations to the gmount of wave rectified as in other rectiers.

It will be appreciated that to obtain extremely short intervals of a rectified wave, my conducting arcs would be very short, and I might use similar spheres on both the homceoids.

I claim:

1. In a high voltage electrical system, the combination with a source of substantially periodically varying high tension current, of a load and a synchronous rectifier comprising a plurahty of electrodes spaced apart substantially equal distances circumferentially, and relatively rotatable arcshaped electrodes having an angular extent in excess of the angular distance between adjacent pairs of said first-mentioned electrodes,-said relatively rotatable electrodes having radii of curvature in two directions of such dimensions as to substantially elim mate corona.

electrodes, measured in mechanical degrees,

during the transmission of current.

Means for rectifying potential ex a half cycle of cess often thousands volts comprising relax tively rotatable electrodes, means for causrevolving and stationary parts, or general ing said electrodes to approach and recede periodically, said electrodes having a contour or configuration adapted toconstantly present approximately flat face portions when opposed and being of such dimensions as to substantially eliminate corona. 4. In a device of the class described, a

high potential rectifier comprising relatively rotatableelectrodes, having curved surfaces adapted to present opposed approximately tangential planes, at points of approach or recession during the relative movement of said electrodes, whereby high voltage energy transfer is effected without.

several percent of the radius of said arcshaped members.

7. A rotary rectifying switch for X-ray apparatus comprising a shaft and a pair of conducting members mounted thereon, said members comprising substantially spheroidal ends connected by an arc-shaped membet, the radii of said ends being at least several per ;cent of the radius of said areshaped members as determined with respect to the shaft on which said members are mounted.

8. Means for rectifying potential in excess of ten thousand volts comprising two sets of electrodes relatively movable with respect to each other, half of the electrodes of one set being connected to said source of current, a load connected to the remaining halfof said electrodes of the same set, the electrodes of said second set bridging adjacent pairs of electrodes of said first set to transmit a portion of the wave under rectification, said cooperating electrodes having a configuration adapted toconsta-ntly present approximately flat face portions, when opposed and being of such dimensions as to substantiall eliminate corona.

9. A rectifier of the class described com near the corona generatin point of the applied'potential under rectification.

10. A rotary rectifying switch for X-ray apparatus, comprising a shaft, a pair of arcshaped conducting members mounted thereon having transversely rounded outer surfaces and spherical ends,said members being arranged on opposite sides of said shaft, and two pairs of stationary conducting members also having spherical surfaces adjacent the path of travel'of said arc-shaped members. i

11. A rotary rectifying switch forX-ray apparatus, comprising a shaft, a pair of arc-shaped conducting member mounted thereon having substantially spherical ends of radii which are several per cent of the length of said member, said members being mounted on opposite sides of said shaft and spaced late-rally from each other to permit rotation in parallel planes, and two pairs of stationary contact members mounted in the plane of and adjacent the path of travel of each ofsaid arc-shaped members, said stationary contacts also having substantially spherical surface portions.

12. In a-high voltage rectifier, electrodes movable relatively to other electrodes, and means for causing such movement, said electrodes bein formed as homoeoids, whereby corona is sli bstantially avoided at operating voltages of the rectifier.

13.' In combination, a transformer, a high potential rectifier and a load, said rectifier comprising a plurality of conducting mem bers connected to said transformer and a plurality of conducting members connected to said load, certain of said members being relatively rotatable to provide an intermittent conducting path for thehigh potential current, and presenting operating surfaces having configurations which substantially prevent corona at operating voltages.

14:.111 a device of the class described, cooperating electrodes having a configuration which presents a rounded contour on substantially all exterior portions whereby corona is substantially eliminated, one of said electrodes being hollow.

, 15. In a device of the class described, a synchronously driven rotor carrying hollow conducting segmental electrodes.

16. In a device of the class described, a synchronously driven rotor, carrying shells with rounded ends and curved to form an arc. I

Ill

trodes having'surfaces of a curvature sufliciently remote from a curvature which generates substantial corona at the applied potential under rectification to substantially eliminate objectionable corona.

19. A high potential rectifier of the class described, comprising relatively rotatable electrodes and means for causing such rotation, certain of said electrodes being of opposite polarity, when current is being rectifled, and being spaced laterally and longitudinally and having surfaces of curvatures sufficiently near the corona point and sufliciently removed from the spark-over point of the electrostatic field of the said curved surfaces to prevent substantial formation of corona in and about said rectifier, under operating voltages thereof.

20. A rotary rectifying switch for X-ray apparatus'comprising a shaft and a pair of conducting members mounted thereon, said members having substantially spheroidal ends, the radii of said ends being at least several per cent of the distance from the extreme outer surfaces of said end to the shaft on which said members are mounted.

21. A high voltage electrical rectifier comprising electrodes, certain of which are rotatable relatively to others, said electrodes being provided with surface characteristic means for collectively reducing the density of the electrostatic field determining the corona formation point at operating voltages. y

22. A high voltage electrical rectifier comprising relatively movable parts, said parts comprising means for equalizing electrostatic field distribution.

MONTFORD MORRISON. 

